This invention relates to the curing of tobacco leaf.
The temperature and humidity in any type of tobacco curer must be properly controlled if the tobacco leaf is to be cured without spoilage in the minimum of time, with the best possible weight in cured leaf of top quality. The curing process is dependent inter-alia on the humidity and on the temperature inside the curer.
Generally the temperature inside the curer is manually controlled according to empirical formulae. Such processes work satisfactorily but however are not generally optimal. It is impossible to increase the temperature in the curer manually precisely as the leaf requires heat. The result of not being able to set the correct temperature at the correct time results in scorching or early dehydration of the leaf, or in loss of weight.
Various solutions have been proposed and described in the literature, see the specifications of U.S. Pat. Nos. 3,503,137; 3,545,455; 3,618,225; 3,624,917; 3,664,034; 3,927,683; 3,937,227; 4,178,946; 4,192,323, and 4,206,554.
The second last of these patents discloses a method for bulk curing tobacco in which the temperature conditions in a curing barn are automatically controlled by heating the air being circulated through the barn in a controlled manner to maintain a predetermined difference in the dry bulb temperature of the air entering and leaving the curing chamber. To achieve this objective temperature sensors are located externally of the barn exposed to the inlet and outlet air flows respectively. As emerges from the disclosure the actual temperature maintained in the barn is largely dependent on the ambient temperature i.e. the temperature prevailing outside the barn. It follows that the curing process is also dependent on the temperature externally of the barn.